The Incomprehensible Dr. S

Have already started studying for an exam on Wednesday in Dr. S's class.

The course is supposed to bring calculus, probability and risk management together. I put about 3 hours of study in for it today, remembering definitions and basically solving problems like the ones found on Exam P.

Boy, am I rusty. It's like I'm forgetting the most basic stuff, like calculating E(x) for a random variable, simple math errors. And Dr. S hasn't really given any direction to his course at all. I've seen a lot of probability, and a tad of risk management and calculus. I don't know what the point of his course is, and no one else seems to know what it is either.

Got some input back on Dr. N's Intro Probability course. (I actually took the sequel to Intro Probability before taking Intro Probability, but that's another story.) Eight problems, 45 minutes. No one got #7 right, which is this:

You have five boxes and five marbles. Each of the five marbles is assigned to a box. Assume that the chances that a marble is assigned to a particular box are equal (i. e., if the boxes are A, B, C, D, and E, then P(marble assigned to A) = ... =P(marble assigned to E)) and each marble MUST be assigned to one box.)

What is the probability that exactly one box will remain empty after all the marbles are assigned?

Can you figure it out? If you can, put the solution in the comments and I'll read it sometime in 2010.